Could it be possible to mod or create a pneumatic gun, but whose pressure and power come from the reaction between Diet Coke and Mentos?

I was thinking of some like adding two ball valves, one after the other, on one end of the "air" chamber. Put some Coke in, then close both ball valves. Open the first to put the Mentos in, close it, then open the second to drop the mentos into the Coke. Then of course open the third ball valve (the one that connects barrel to chamber) to launch it.